Distributor Vacuum Canister—Testing A Reproduction Canister – Discussion Finale

Some time has passed since this Discussion began. We tested and tested some more.

To review: Hendrik “Hank” Blommers of Canada discovered a source for Vacuum Canisters which have the appearance of those used from 1966 through 1970 on Stock Bosch Distributors.

He contacted Eric Shoemaker—1967beetle.com –to see if Eric knew of a way to test a Reproduction Canister.

As a result, Hank mailed an example Canister to me to test. Thus began a series of 3 Articles on the subject of Distributor Testing equipment and comparative testing of Distributors with Stock, Vintage Bosch Canisters and with the Reproduction Canister.

Here, I believe, is the result, after much testing and discussion among Adam Troeger, Kurt Troeger, Hank Blommers and me. It is not completely straight-forward due to several variables which we cannot completely control. But this seems to be the consensus.

First—there still are plenty of original Bosch Canisters available in private collections and in salvage yards. This seems to be true—although, sometimes it is difficult to find the exact part needed.

This, coupled with the fact that Bosch did NOT mark all of their Canisters either with Part Numbers or other identifying signs. This proved to be very frustrating, even though we did find a table which details which Canisters go with which Distributors. With few-to-no identifying markings on the Canisters, this Table proved to be of little practical value.

As a result, even though one may have a Vintage Vacuum Canister which has the appearance of a stock Canister which should go with the above mentioned range of Distributors, we found it necessary to test each Vintage Canister on a given Distributor, using the Distributor Testing Equipment in order to obtain information which would allow us to pair Canisters and Distributors. Once we obtained a proper “pair”, we would be able to demonstrate the correct “range of operation” which was predicated by Bosch Operating Standards Tables for that pair (for a given application).

For instance–we could arrive at a proper pairing of a Vacuum Canister with a 113-905-205K (1966 through 1967 Beetle Distributor), obtaining the correct operational capacity.

The long and the short of it was that we never could arrive at an acceptable paring by using the Reproduction Canister.

This could be true for various reasons:

  • The Diaphragm of the Reproduction Canister is of unknown value as to its capabilities—stronger? weaker? different material? different diameter? –from the original Bosch Vacuum Canister Diaphragms.
  • The Operating Rod (or Arm) of the Reproduction Canister is of a different length and the stops are placed differently from those of the Bosch Rods.

Furthermore—we discovered a difference among the original Bosch Points Plate Return Springs. These differences included Spring wire diameter, diameter of the Springs; the number of “turns” of the wire, Spring lengths; other?

We used Springs with different attributes and found that we could achieve different results—with both the Original Bosch Canisters AND with the Reproduction Canister.
We surmised that if were we able to obtain a stock of Return Springs of differing values/characteristics, we might be able to achieve better results by substituting them for the Bosch Return Springs to use when testing the Reproduction Canister. (trial and error style testing)

Obtaining quantities of Springs of different characteristics is a vague and difficult endeavor.

Then, there is the matter of the Eccentric Return Spring Post. As you will recall, I had a Tool fabricated which allows this Eccentric Post to be rotated in order to obtain more or less tension upon the Return Spring. Similar to shortening or lengthening the Spring.

What’s the analysis here?

Regarding the 113-905-205K Distributor for 1966-1967 Beetles:

Obtaining and installing a Reproduction Canister (of the type which we studied) will not result in achieving Proper Operational Specifications.

Repeating what we state above: The Operating Rod (or Arm) of the Reproduction Canister is of a different length from the Rods on Vintage Distributor Vacuum Canisters—namely shorter. This Rod differential, alone, proves to be the nemesis.

There is an approximately 7mm Working Length difference between the Original Bosch Operating Rod (Arm) and the Operating Rod (Arm) of the Reproduction Canister.

Theoretically, a person could cut-and-weld an extension into the Reproduction Canister’s Rod. In reality—this is not going to happen.

It is remotely possible that a person could “work around” the other problems, but Operating Rod Length puts an end to speculation.

We gave it our best. We hated to “give up”—but the facts are there.

If we could, we would ask the manufacturer why more care was not given when analyzing Original Equipment before setting out to reproduce a Canister. In this Technical Age when anything seems to be possible, we continue to see reproduction parts for our Volkswagens which don’t correspond to original factory parts.

Bottom Line: Save integral vintage parts. Follow my example: I have considered those parts which are most likely to fail, and I have stored sound examples in a special closet in our garage. This includes a rebuilt 113-905-205K Bosch Distributor alongside a 30 Pict-1 (VW 105-1) German Solex Carburetor. (plus myriad other parts).

I have included these integral, spare parts under my Vintage/Collector Car Insurance. Ask your Insurer to insure the spare parts which you may have stock-piled.


Again, I want to thank David Brown for making available the Sun Diagnostic Testing Equipment. We would have been at a loss, otherwise.

I want to thank Adam Troeger who spent a LOT of time testing, then retesting and coming to conclusions as a result. He is to be congratulated for renewing the Diagnostic Testing Equipment and for using it in a suitable and responsible manner.

Thank you, Kurt Troeger, for transporting the equipment and assisting in the experiments.

A Big Thanks goes to Hendrik “Hank” Blommers for sourcing, purchasing and making the Reproduction Vacuum Canister available. What a journey, Hank! I wish that you had been here to personally experience the testing and the in-depth conversations which ensued!

Reference The Three Previously Published Distributor Articles Relating To This Subject:

Passing The Baton – A Vintage Sun Distributor Testing Station

Distributor Vacuum Canister Comparisons – Are Reproduction Canisters The Answer?

Distributor Points Plate Return Spring Eccentric Post

Posted by Jay Salser

My wife, Neva, and I have been driving and working on VWs since 1976. In fact, we raised our family in these cars. Now, we are retired and enjoy VWs as a hobby. The ’67 Beetle always has been our favorite year. We own a '67 Beetle and a '68 Karmann Ghia.

  1. Good one, JK!

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